Most catalysts in preparing carbon nanofibers by chemical vapor deposition are transition metals such as Fe,Co and Ni.However,strong acids must be used to purify the products.This process requires high-level equipments and part of impurities can not be removed easily.In this study,carbon nanofibers were obtained by chemical vapor depostiton using water-soluble K2CO3 as catalyst,which were obtained by two methods: precursor and micro-emulsion,using acetylene(C2H2) gas as carbon resource.The results showed that the precursor method was better to synthesize the carbon nanofibers and 600 ℃ is the optimal temperature,under which helical carbon nanofibers were obtained.Under 700 ℃,linear carbon nanofibers were obtained.